Alcohols, C9-11, branched and linear, ethoxylated, sulfates, ammonium salts

Dissociation constant

Link to relevant study record(s)

Reference

Endpoint:

dissociation constant

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2 Apr 2012

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 112 (Dissociation Constants in Water)

GLP compliance:

no

Dissociating properties:

yes

No.:

#1

pKa:

1.24

Temp.:

20 °C

Remarks on result:

other: Mean of two determinations A and B

Sample measurements, solutions A and B:

Dilution factor	Solution A, concentration, g/L	Solution A, conductivity, µS/cm	Solution B, concentration, g/L	Solution B, conductivity, µS/cm
0	5.018	1115	4.290	984
2	2.509	638	2.145	551
4	1.2545	329	1.0725	281.7
8	0.62725	169	0.53625	144.3
16	0.313625	86.2	0.268125	73.8
32	0.1568125	43.8	0.1340625	37.5
64	0.07840625	22.49	0.06703125	19.34
128	0.03920313	11.91	0.03351563	10.33

Solution A:

Concentration solution A, g/L	Concentration solution A, mol/L	Specific conductivity k, mS/cm	Equivalent conductivity L, S cm^2/mol	Reciprocal equivalent conductivity 1/L, mol/S cm^2
5.018*	0.0130677	1.115	85.3248	0.01171992
2.509	0.0065339	0.638	97.6453	0.01024115
1.2545	0.0032669	0.329	100.7063	0.00992987
0.62725	0.0016335	0.169	103.4611	0.00966546
0.313625	0.0008167	0.0862	105.5426	0.00947485
0.1568125	0.0004084	0.0438	107.2568	0.00932342
0.07840625*	0.0002042	0.02249	110.1463	0.00907883
0.03920313*	0.0001021	0.01191	116.6601	0.00857191

* - concentration neglected for calculations

1/L = a*k + b, slope a = 0.0014831, intercept b = 0.0093514

Ostwald dilution law: K_a = 1/(a*(1/b)²) = 0.059; pK_a = - log K_a = 1.23

Solution B:

Concentration solution B, g/L	Concentration solution B, mol/L	Specific conductivity k, mS/cm	Equivalent conductivity L, S cm^2/mol	Reciprocal equivalent conductivity 1/L, mol/S cm^2
4.290*	0.0111719	0.984	88.0783	0.01135353
2.145	0.0055859	0.551	98.6406	0.01013782
1.0725	0.0027930	0.2817	100.8604	0.00991469
0.53625	0.0013965	0.1443	103.3309	0.00967765
0.268125	0.0006982	0.0738	105.6940	0.00946128
0.1340625	0.0003491	0.0375	107.4126	0.0093099
0.06703125*	0.0001746	0.01934	110.7925	0.00902588
0.03351563*	0.0000873	0.01033	118.3543	0.0084492

*- concentration neglected for calculations

1/L = a*k + b, slope a = 0.001531, intercept b = 0.009367

Ostwald dilution law: K_a= 1/(a*(1/b)²) = 0.0573; pK_a= - log K_a= 1.24

Average pK_a= 1.24.

Description of key information

pKa = 1.24 at 20 °C

Additional information

The dissociation constant of the substance was determined according to OECD Guideline 112 (conductometric method).